When the Fluke DMM ECHO setting is on, the following happens using the VISA test panel in NI MAX:
- From the VISA panel, a write command is sent to write *IDN?\r to the multimeter. No error, the DMM accepts the command.
- From the VISA panel, a read command is sent, and the DMM echos the previous write (*IDN?\r) command back to the VISA panel
- From the VISA panel, a read command is sent, and the DMM reports the result of the write command (FLUKE, 45, [sn redacted], 1.7 D1.0\r\n)
- From the VISA Panel, a read command is sent, and the DMM reports that the write command was received and executed successfully using the DMM's default nomenclature (=>\r\n)
Note that this is entirely the same when the ECHO setting is off, except that step 2 does not occur.
Now, this is entirely the same as the following output when issuing the *IDN? command in Tera Term:
*IDN?
FLUKE, 45, [sn redacted], 1.7 D1.0
=>
(Tera Term, does not display the carriage return (\r) or line feed (\n) like the VISA panel does.)
So, it would appear that the VISA panel is communicating with the DMM in the same way as terminal, it is just not actively reading like Tera Term and requires the user to request a line read.
What I do not understand, is the difference between behavior of the DMM when using Tera Term or the VISA test panel and when using LabVIEW.
When communicating with the DMM in Tera Term or the VISA Panel, the DMM responds by going from display state 1 to display state 2 (see images below). When attempting to use even the most basic example serial communication VIs or the Fluke plug and play driver VIs, the DMM stays at display state 1. Note that the change from state 1 to state 2 happens only after initiating a connection in Tera Term or the VISA panel; so, I believe that I am experiencing an issue where LabVIEW is unable to acquire a communication lock with the serial instrument.
If anyone has insight, please let me know if you have any way to troubleshoot this particular issue.
Display State 1:
Display State 2:
